Protests were held at the University of California at Riverside, at a Republican congressional office in Irvine and at UC Irvine, among other locations.
In Riverside, several hundred students protested Trump's order, in addition to his plan to build a wall on the U.S.-Mexico border.
In Irvine, one protest was held at the office of Republican Congresswoman Mimi Walters.
Another was held at UC Irvine.
The school has 154 students who hail from the seven countries on the Trump executive order. The school has advised its students from those countries not to travel outside the United States for now.
Students at the protest said they wanted to send the message that UCI is a safe place for students from Muslim countries.
"There's a little bit of fear, but also a lot of hope that we'll overcome this," said student Sara Boukai. "We'll be able to get through this and show that our voices together are so much louder than anybody."